A member says that he took over a client's Web site from an other SEO. He noticed that the client's ranking in Yahoo dropped. He also noticed that the content in the title tags are not grammatically correct. If you put one and one together, it can imply that your rankings will tank in Yahoo if your title tag is not in proper English.

But that is absolutely wrong. Most title tags don't read 100% grammatically correct, some times on purpose. It is important it reads quickly and catchy and sometimes that means you need to put grammar on the back burner.